Oil burner having a combustion aid



Dec. 21, 1965 H. SKONECKE ETAL 3,224,488

OIL BURNER HAVING A COMBUSTION AID Filed Oct. 11, 1962 INVENTOR. ,L/M X. Jim

W 17. KM ram 5 Jn a A TTORNE Y United States Patent OIL BURNER HAVING A COMBUSTION All) Hubert L. Skonecke, Chicago Heights, 111., James H. Kirk,

Dyer, Ind., and Donald E. Safford, Park Forest, 11].,

assignors to Sinclair Research, Inc., Wilmington, Del., a

corporation of Delaware Filed Oct. 11, 1962, Ser. No. 229,929 6 Claims. (Cl. 15873) This invention is a novel combustion aid for use with a liquid fuel burner. In liquid fuel burners, such as the ordinary gun-type domestic fuel oil burner, the invention serves to insure proper contact of fuel and combustion supporting gas and to steady or stabilize the combustion.

The gun-type liquid fuel burner has for many years been accepted as the standard domestic fuel oil burner. This type of burner generally comprises a fuel oil pump and line ending in an atomizing nozzle, and an air pump which supplies combustion-supporting gas to the atomized fuel. Generally, a barrel-type conduit is supplied for the air and the fuel conduit is arranged concentrically within the air barrel, with the fuel nozzle recessed slightly within the exit end of the air barrel. In operation, it is conventional to so proportion the flow of liquid hydrocarbon fuel and combustion supporting gas that little, if any, surplus gas is supplied. In this way pumping costs and the size of equipment are reduced and the cooling effect of excess gas is minimized. This control over the proportions of fuel and gas makes good mixing of the fire components and stabilization of the flame essential, and almost universally the air barrel is provided with a nose cone or its equivalent flow director. The flow of air and fuel within the conduits provided is generally parallel, but downstream of the nozzle the flow of each fluid is generally altered to provide a mixing and combustion zone. Such mixing may be brought about by the use of an atomizing fuel nozzle which sprays the fuel into the mixing zone perhaps somewhat in the form of a cone. The constriction of the end of the air barrel by an end cone serves to deflect the air flow inwardly into admixture with the cone-shaped fuel spray. Ignition can be performed by electrodes which are within the mixture of air and atomized fuel. The gun directs the resulting flame into a combustion chamber or furnace where indirect heat exchange between the hot combustion products and the domestic heat exchang fluid is performed.

Such gun-type fuel-oil burners, which operate with air at or near atmospheric pressure, provide good efliciency to a domestic system in at least two respects; viz, in needing only the two pumps as moving parts and keeping most elements of the burner out of the way of the hot flames, and in producing a good deal of heat in the combustion chamber very quickly upon demand. The combustion efliciency of the gun-type burner, however, is susceptible to improvement; for example, even though the nozzle may be finely adjusted to give the proper degree of atomization, momentary fluctuations in the oil supply may occur, tending to cause pulsations of the flame and to create a .rless-than-ideally dispersed supply of fuel along the axis of the cone spray. Also, strong air currents from outside the furnace may unduly deflect or even put out the flame. In either event, an over-supply of fuel is likely to pass through the combustion zone incompletely vaporized and/ or incompletely burned, creating smoke and cutting down on the combustion efficiency of the burner.

Ordinarily, the domestic fuel oil burner provides for ignition of the fuel air mixture by means of an electrode are which operates on a thermostatic principle. Thus the electrode circuit is provided with sensing means which, on perception of the heat from a burner flame, cuts off the electrode current. If a momentary over-supply of air to the burner occurs, the resulting lowering of temperature may cause loss of the flame. The sensing means in this invention will reestablish the electrode current to reignite the fuel and gas mixture, but fuel values will be lost during the time that combustion is interrupted.

This invention aids combustion in a number of ways: it assures better mixing of the fuel with combustion supporting gas and overcomes the effects of momentary overor under-supplies of fuel or combustion supporting gas by acting both as a fuel and a heat reservoir. It focuses the flame to avoid flame pulsation by providing a surface on which fuel from momentary floods of unvaporized liquid particles or small clouds of vapor supersaturated with fuel may coalesce. The combustion aid of this invention also provides a further surface, downstream, accessible to combustion supporting gas which flows around the combustion aid. The coalesced fuel may travel to this downstream surface to be vaporized and mixed with further amounts of combustion supporting gas. By thus spreading fuel out into that area downstream of the combustion zone where there is likely to be a greater supply of air, despite the agitation brought about by the end cone, this invention serves for better utilization of this air by allowing the coalesced fuel to revaporize more homogeneously in the combustion supporting gas.

The combustion aid of this invention comprises a ballshaped member having a substantially continuous surface, placed just downstream from the zone, at the end of the air barrel, where the most vigorous mixing of the fuel and combustion supporting gas occurs. Preferably the member is coaxial with the nozzle of the fuel burner and covers only a minor portion of the cross-sectionof the combustion zone of the burner, that is, less than half of the flow space cross-section downstream of the fuel nozzle. Although it may be hollow, the member is preferably solid and is advantageously made of metal but may comprise other non-porous solid materials, such as ceramics, which will withstand deformation at the temperatures of the combustion.

By ball-shaped is meant that the portion of the solid member which faces the fuel nozzle is substantially continuous and spherical in form. By thus directing a spherical portion of the combustion device at the fuel nozzle, the combustion aid of this invention appears to intercept imperfectly atomized droplets of liquid fuel, probably causing them to coalesce on the sphere. It is reasoned that the coalesced fuel, under the influence of continued gas flow from the nozzle and air barrel, is pushed around to the leeward side of the combustion aid where, it may be vaporized uniformly into the accessible and still-hot gas stream for quick and complete combustion. A number of properties of the combustion aid of this invention contribute to this vaporization, for example, the heat absorbed on the leading surface of the sphere and conducted to the downstream surface, the effect of combustion gas flow along the downstream surface or, alternatively, the venturi effect of combustion gas flow slightly above this downstream surface. The back or vaporization surface of the device may therefore be such as to complete a ball, or may be conical, etc. Preferably this surface is other than flat in order to provide maximum vaporization surface.

The device of this invention gives a better combustion effect than the so-called flame-holders known to the art. These prior devices serve as heat reservoirs during momentary interruptions of fuel flow; however, they also serve to coalesce improperly atomized fuel and hold it within the primary gas stream. In operation, hydrocarbon fuel coalesced on such devices frequently serves to reduce the carbon monoxide or carbon dioxide combustion gases, converting both gas and fuel to water and free carbon. This free carbon is usually Wasted in the gas stream and further, creates a smoke nuisance. The combustion aid of this invention avoids this effect by providing for conducting away the coalesced fuel from the main combustion zone. The combustion aid may be hollow or filled with the same or a different material from the surface material, preferably a heat conductive material. It can be seen that the combustion aid of this invention besides serving to assure combustion of over-supplies of fuel, also serves as a heat reservoir during momentary under-supplies of fuel, and thus helps to stabilize the flame, while providing for more thorough exploitation of fuel values once it has warmed up.

The solid member is generally supported by arms which extend from the fuel nozzle. For ease of replacement, the arms will generally be rigidly fastened to an adapter, for example, a collar which fits around the standard fuel nozzle assembly and which may be supported thereby.

The invention will be better understood by reference to the accompanying drawing which is to be considered illustrative only and not limiting. In the drawing,

FIGURE 1 is a perspective view of a liquid fuel burner equipped with the device of this invention with the air barrel and nose cone shown in phantom lines; and

FIGURE 2 is a modified version of the solid member of this invention with its support.

Conventionally, the liquid fuel burner will consist essentially of the fuel line 6, the nozzle 8 and the electrodes 10 and 12, which have the insulated leads and 17, respectively. The member 20, having the ballshaped portion 22 directed toward the fuel burner nozzle has its downstream surface in the form of a cone 25 in FIGURE 1 and in the form of a hemisphere 27 in FIGUIUE 2. The combustion aid generally is supported on the nozzle 8 by means of the arms 30 and 33 which extend between the member and the collar 36 which may be affixed to the nozzle 8 by means of the set screw 39.

As can readily be seen, the device of this invention can easily be installed on existing gun-type liquid fuel burners by putting the collar around the nozzle adaptor and fastening it with the set screw. The length of the arms supporting the solid member is often sufficient to place the member just beyond the zone of greatest turbulence which occurs immediately downstream of the fuel nozzle. Generally, this length will place the solid member a distance in front of the fuel nozzle at least about twice the distance from the fuel nozzle to the exit edge of the end cone, preferably about 2 to 3 times the distance from the fuel nozzle to the exit edge. For example, the solid member of this invention has been found effective when placed about 'Ms" downstream from the fuel nozzle of a burner wherein the nozzle was set back of the exit edge of the end cone.

As described above, the member usually extends outwardly from the axis of the nozzle a distance sufficient to intercept unmixed combustion supporting gas in a zone annular to the fuel-rich zone. In general, the lateral ex tent of the solid member will be almost equal to the opening in the end cone.

In operation, the collar is placed around the nozzle adapter, the member is set in proper distance from the fuel nozzle and flow of air and fuel is begun. High voltage current is sent to the electrodes which are in the mixture of fuel and air. Current is cut off after ignition is assured. Uncombusted fuel and air impinge on the solid member, causing coalescence of excess fuel. The fuel spreads along the surface of the solid member and is It can be readily seen that this invention aids combustion by stabilizing the flame and by assuring better mixing of the fuel with combustion supporting gas downstream of the zone of greatest mixing where the ordinary gun-type burner, despite the atomizing effect of the nozzle and the agitating effect of the nose cone, may still provide too rich a fuel mixture. The invention serves to give stabilized and steady combustion by acting as a heat reservoir to give uniform combustion despite minor fluctuations in fuel or combustion gas flow or vaporization, and also serves to spread out the combustion zone.

It is claimed:

1. In a gun-type liquid fuel burner having a nozzle surrounded by an air conduit and having ignition means downstream of said nozzle, said nozzle being adapted to spray fuel into a mixing zone containing a combustion supporting gas, the improvement which comprises a member in the path of the fuel flow downstream of the nozzle, said member supported by arms extending from the nozzle, said member having a continuous spherical surface in the direction of the nozzle and an inwardlytapered, conical surface downstream of the spherical surface, accessible to said combustion-supporting gas.

2. The burner of claim 1 wherein the arms are fastened to the nozzle by means of a collar which fits around the nozzle and is supported thereby.

3. The burner of claim 1 wherein said ignition means is a pair of electrodes.

4. In a gun-type liquid fuel burner having a nozzle, an air conduit surrounding said nozzle and ignition means, said air conduit having an exit edge downstream of the nozzle and said nozzle being adapted to spray fuel into a mixing zone containing a combustion-supporting gas, the improvement which comprises a member in the path of the fuel flow downstream of said nozzle and ignition means, said member having a continuous spherical surface in the direction of the nozzle and an inwardlytapered, conical surface downstream of the spherical surface accessible to said combustion-supporting gas, and said member having means for attachment to said nozzle.

5. The burner of claim 4 wherein said ignition means is a pair of electrodes.

6. The burner of claim 4 wherein the continuous spherical surface in the direction of the nozzle is a distance in front of the nozzle at least about two times the distance from the fuel nozzle to the exit edge of the air conduit.

References Cited by the-Examiner UNITED STATES PATENTS 714,722 12/ 1902 Macleod 15 873 X 1,086,405 2/1914 Salsich 15873 2,220,603 11/ 1940 Hirtz 158--73 2,361,871 10/1944 Roberts 15873 X FOREIGN PATENTS 22,827 5/ 1936 Australia. 596,448 8/ 1925 France.

JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, JR., PERCY L. PAT- RICK, MEYER PERLIN, Examiners. 

1. IN A GUN-TYPE LIQUID FUEL BURNER HAVING A NOZZLE SURROUNDED BY AN AIR CONDUIT AND HAVING IGNITION MEANS DOWNSTREAM OF SAID NOZZLE, SAID NOZZLE BEING ADAPTED TO SPRAY FUEL INTO A MIXING ZONE CONTAINING A COMBUSTION SUPPORTING GAS, THE IMPROVEMENT WHICH COMPRISES A MEMBER IN THE PATH OF THE FUEL FLOW DOWNSTREAM OF THE NOZZLE, SAID MEMBER SUPPORTED BY ARMS EXTENDING FROM THE NOZZLE, SAID MEMBER HAVING A CONTINUOUS SPHERICAL SURFACE IN THE DIRECTION OF THE NOZZLE AND AN INWARDLYTAPERED, CONICAL SURFACE DOWNSTREAM OF THE SPHERICAL SURFACE, ACCESSIBLE TO SAID COMBUSTION-SUPPORTING GAS. 